The tumor microenvironment determines development and progression of many cancers. Epithelial–mesenchymal transition (EMT) is fundamental to tumor progression and metastasis not only by increasing invasiveness but also by increasing resistance to cell death, senescence, and various cancer therapies; determining inflammation and immune surveillance; and conferring stem cell properties. It does this by enabling polarized epithelial cells to transform into cells with a mesenchymal, and therefore motile, phenotype. Tumor-associated macrophages (TAMs) are key cells of the tumor microenvironment that orchestrate the connection between inflammation and cancer. Activation of EMT often requires crosstalk between cancer cells and components of the local tumor microenvironment, including TAMs. In this review, clinical and experimental evidence is presented for control of TAMs in promoting cancer cell invasion and migration and their interaction with the EMT process in the metastatic cascade. The translational significance of these findings is that the signaling pathways that interconnect TAMs and EMT-modified cancer cells may represent promising therapeutic targets for the treatment of tumor metastasis.
Despite the introduction of many novel therapeutics in clinical practice, metastatic renal cell carcinoma (RCC) remains a treatment-resistant cancer. As red and processed meat are considered risk factors for RCC, and a vegetable-rich diet is thought to reduce this risk, research into plant-based therapeutics may provide valuable complementary or alternative therapeutics for the management of RCC. Herein, we present the antiproliferative and antiangiogenic effects of maslinic acid, which occurs naturally in edible plants, particularly in olive fruits, and also in a variety of medicinal plants. Human RCC cell lines (ACHN, Caki-1, and SN12K1), endothelial cells (human umbilical vein endothelial cell line [HUVEC]), and primary cultures of kidney proximal tubular epithelial cells (PTEC) were treated with maslinic acid. Maslinic acid was relatively less toxic to PTEC when compared with RCC under similar experimental conditions. In RCC cell lines, maslinic acid induced a significant reduction in proliferation, proliferating cell nuclear antigen, and colony formation. In HUVEC, maslinic acid induced a significant reduction in capillary tube formation in vitro and vascular endothelial growth factor. This study provides a rationale for incorporating a maslinic acid–rich diet either to reduce the risk of developing kidney cancer or as an adjunct to existing antiangiogenic therapy to improve efficacy.
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